FUTURE FARMS: High-Rise, Beach Pod, and Pyramid Pictures

Gordon Graff at the University of Waterloo in Ontario thinks his 59-story Skyfarm concept clears what some critics deem an insurmountable hurdle to vertical farms--generating enough electricity to replicate the sun's output at a reasonable cost.

Although the hydroponic farm would consume an estimated 82 million kilowatt hours a year, according to the Toronto Star, an onsite biogas plant burning methane from farm waste would provide about 50 percent of that energy. The rest of the needed fuel could come from city waste.